Eligible subjects must have completed 6 doses of treatment of radium-223 dichloride and experienced no radium-223 dichloride-related SAEs (serious adverse events) or CTCAE (Common Terminology Criteria for Adverse Events) Grade 3 or 4 adverse event during or after the initial course of radium-223 dichloride that led to the discontinuation of treatment. 40 Subjects will be enrolled and will receive up to 6 doses of radium-223 dichloride 50 kBq/kg IV every 4 weeks.